What is the most idiomatic way to get some form of context to the yacc parser in goyacc, i.e. emulate the %param command in traditional yacc?
I need to parse to my .Parse function some context (in this case including for instance where to build its parse tree).
The goyacc .Parse function is declared
func ($$rcvr *$$ParserImpl) Parse($$lex $$Lexer) int {
Things I've thought of:
$$ParserImpl cannot be changed by the .y file, so the obvious solution (to add fields to it) is right out, which is a pity.$$Lexer is an interface, I could stuff the parser context into the Lexer implementation, then force type convert $$lex to that implementation (assuming my parser always used the same lexer), but this seems pretty disgusting (for which read non-idiomatic). Moreover there is (seemingly) no way to put a user-generated line at the top of the Parse function like c := yylex.(*lexer).c, so in the many tens of places I want to refer to this variable, I have to use the rather ugly form yylex.(*lexer).c rather than just c.%param in normal yacc / C (well, bison anyway), but that doesn't exist in goyacc..go file with sed or perl for what are hopefully obvious reasons.What's the most idiomatic solution here? I keep thinking I must be missing something simple.
My own solution is to modify goyacc (see this PR) which adds a %param directive allowing one or more fields to be added to the $$ParserImpl structure (accessible as $$rcvr in code). This seems the most idiomatic route. This permits not only passing context in, but the ability for the user to add additional func()s using $$ParserImpl as a receiver.